Conventionally, there have been dehumidifying apparatuses that combine a desiccant for adsorbing and desorbing moisture with a heat pump. For example, a dehumidifying apparatus is proposed, which defines an air passage to allow air currents of different relative humidities to pass through a rotor-like desiccant material and rotates the desiccant material to repeat an adsorption reaction and a desorption reaction (see, e.g., Patent Literature 1). At a low temperature (e.g., 10 degrees C.), the dehumidifying apparatus described in Patent Literature 1 causes air heated by a heater to flow into the desiccant material to promote transmission of moisture. This increases the humidity and the amount of humidification, so that passage of the heated air through an evaporator raises the evaporation temperature and suppresses frost formation on a heat exchanger.